Biochemical and structural characterization of novel metalloprotein sensors and carboxypeptidases

by Isaza, Clara Eugenia

Abstract (Summary)

The focus of the research that I carried out during my Ph.D. was the characterization of three metalloproteins. The characterization was based on the information obtained from their structures and biochemical data obtained from in-vitro and in-vivo experiments. The structures of the three proteins studied were obtained by x?ray crystallography. The first protein studied was the hemerythrin-like domain from the Desulfovibrio vulgaris chemoreceptor H. To be able to propose a role and the mechanism by which this domain works, we solved the structures of the protein in the three physiological relevant states. The proposed mechanism is based on the observed differences between the three states. The second protein studied was the Bacillus subtilis M32 carboxypeptidase, BsuCP. The activity of this enzyme was tested with different substrates to learn about its specificity and the length of substrates on which it acts. The structure of the protein was solved to understand the properties that influence its activity. The third aim of this Ph.D. work was the study of another M32 carboxypeptidase, LmaCP, which is found in Leishmania major. The substrate specificity for LmaCP was studied by enzymatic assays. To propose a physiological role for this enzyme, its expression profile in the three main life stages of the L. major protozoa was examined. We were able to used the previously solved crystallographic structure of LmaCP (solved previously by this laboratory (Zhong et al, unpublished results)) to compare it with the BsuCP structure to explain the activity differences found between these two members of the M32 family of carboxypeptidases.